An example of a controlled device may be found in the connected lighting landscape, where connected lamps or lighting devices are controlled by a central unit. In the connected lighting landscape, there is an ongoing price battle mainly for connected (tunable) white dimmable lamps. For these lamps, the volumes are expected to become very large which makes the Bill of Material (BOM) cost very important. Currently one is already at a point where connectivity is a significant factor of BOM cost in a connected white dimmable lamp.
Such cost advantages might also be beneficial to other lights (color lamps, luminaires etc.).
An important cost driver for such a device/product is non-volatile random access memory (NVRAM, e.g. flash memory). Reasons for this include its relatively large (semiconductor) area and additional mask steps needed in production.
Not having to include such cost driver, i.e. to provide a chip without any NVRAM but only non-volatile read only memory (ROM) might be very cost advantageous.
However, a connected light (or any other example of a controlled device) is not always powered.
Conventionally, in order to avoid a need for a fresh configuration process entering the connected light into the framework of the system each time the connected light is powered up again, NVRAM is used to make sure that the connected light maintains the configuration information and thus stays part of a wireless network (in particular “remembers” the access to the wireless network) and is provided with application features which persist over power cycles. For example a light may persistently store a network address, network security key and frame counter to operate in a secure network and it may store scenes, groups, last light state for light control and other information. Often it also can store a new version of its own program to be software upgradable.
A straightforward approach on avoiding a need for frequent fresh configurations might include avoiding the (complete) powering down of the controlled device altogether, e.g. by means of a separate small power source powering only the always static or dynamic random access memory. However, such approach is neither efficient in terms of power consumption, use of resources, product lifetime or price nor even feasible under many conditions.